Brake adjusting mechanism



Aug. 28, 1 951 P. c. WILSON BRAKE ADJUSTING MECHANISM Filed Oct. 26,1948 2 Sheets-Sheet l INVENTOR J Palmer C/yoe Wilson 465 wt? M31Patented Aug. 28, 1951 UNITED STATES PATENT OFFICE 7 Claims.

This application relates to a brake adjuster for brakes of the typehaving a drum affixed to a rotating member and a shoe which is pivotedto a fixed support and which is pressed against the drum to obtainbraking action. My brake adjuster is especially intended for wheelbrakes on automobiles and trucks and therefore it will be described withreference thereto.

It is obviously desirable that automobile brakes act as quickly aspossible whenever the driver applies the brakes. Accordingly, only avery small clearance is provided between the drum and the shoe when thebrakes are released. Generally, this clearance is one ten-thousandth ofan inch. Consquently, when an automobile driver applies the brakes bypressing a brake pedal only a slight amount of travel of the pedal isrequired to obtain braking action provided, of course, the hydraulicsystem or the mechanical linkage between the pedal and the brakes is inproper operating condition.

As the shoes wear from use, however, the shoes must be moved more thanthe normal amount to contact the drum and the driver must move the brakefoot pedal a corresponding further dis tance. Quick braking action,therefore, cannot be obtained. I provide a construction wherebyautomatic compensation can be made for the wearing of the shoes so thatquick braking action can be obtained at all times. I employ a simplemechanical construction which, when the brakes are released, maintainsthe proper clearance between the drum and shoes. I provide bars slidablyheld by the fixed support on which the shoes are pivoted, which barsmove with the shoe only in one direction, 1. e., towards the drum, andwhich prevent movement of the shoe away from the drum beyond theprescribed clearance between the shoes and the drum.

In the accompanying drawings I have illustrated a present preferredembodiment of my invention, in which Figure 1 is a front elevationpartially in section of an automobile brake embodying my invention, thesection being taken on the lines I--I l of Figure 2;

Figure 2 is a horizontal section on the lines 11-11 of Figure 1;

Figure 3 is a fragmentary view similar to Fig ure 1 but on an enlargedscale;

Figure 4 is a section along the lines IV-IV of Figure 3;

Figure 5 is a fragmentary section similar to Figure 1 but showing thebrakes released;

Figure 6 is a section along the lines VI-VI of Figure 4; and

Figure 7 is a detail view of the bar and shoe.

Figure 1 shows an automobile wheel brake having a drum 8 which issecured to an automobile wheel by means, for example, of a hub 9. Aplate I 0 secured to an axle housing H (in the case of the rear wheel ofan automobile) or secured to a stationary part of a front axle sup portsbrake shoes l2. The shoes are pivoted to the plate I!) about pins l3.The other ends of the shoes carry short pins [4 which extend into theopen ends of a wheel cylinder I5 and engage pistons [6 in the cylinder.Each shoe I2 comprises a plate I! having a central reinforcing flange H3and a lining l9 which actually engages the drum 8. When the automobiledriver applies the brakes, he presses a foot pedal which supplies fluidunder pressure to the wheel cylinder [5 through the opening 20 by apiston and cylinder and conduit not shown. The pistons l6 move outwardlyin the cylinder and thus rotate the brake shoes about the pins I 3 toengage the drum. When the brakes are released wheeisprings 21 secured tothe flanges I8 of the shoes and to my brake adjuster, as willhereinafter be described, withdraw the shoes from the drum and forcefluid out of the wheel cylinder [5. With the exception of the connectionof one end of the wheel springs 2| to my adjusting mechanism, the partsso far described are conventional.

Figures 3, 4 and 5 show my brake adjuster in detail. The adjustercomprises a base 22 secured to the plate I0 and having flanges 23 whichextend at right angles to its outer surface to form a channel or guidefor each of two bars 24, one of which is provided for each shoe. Eachbar 24 has a pin 25 adjacent its end near the shoe. Each pin has anenlarged portion or stud 26 which extends through an opening 27 formedin the flange [8 of the shoe. As appears in Figures 3 and 7 of thedrawings, the enlarged portion or stud 26 is oval in cross-section andthe opening 21 in the flange I8 is circular, the major axis of the ovalstud 26 being very slightly less than the diameter of the opening 21. Asis best shown in Figure 7, there is thus a small lateral clearancebetween the stud 25 and the opening 21. For reasons later explained, theclearance between the stud 26 and the opening 21 is the same as theprescribed clearance between the drum 8 and the lining I9 of the shoeswhen the brakes are released.

A pin 28 extends from the base 22 between the flanges 23 and through alongitudinal slot 29 formed. in each bar. The pin also passes through aplate 30 which is placed against both of the bars 24. The end extendingbeyond the plate 30 is flattened to provide a pivot point for a camlever 3! which is slotted to fit over the flattened end of the pin 28and which rotates about a pin 32 extending transversely through the pin28 and the lever 3|. As appears in Figures 4 and 6, the cam lever 6! ispivoted adjacent one end so as to provide a long and a short lever arm.The short lever arm is rounded as at 33 to engage the plate 38 when thelever is rotated clockwise viewing Figure 5. The long arm of the lever3| has a hole 34 through which one end of a wheel spring 2! isconnected. v

The springs Z! are connected to the brake shoes and to the cam levers sothat they are under tension even when the brakes are not ap plied. Sincethe springs pull on the long arms of the levers 3|, the short arms ofthe levers press against the plate 3!! with considerable force and thatplate in turn presses against the bars 24 to clamp them to the base 22between the flanges 23. The levers 3i and the plate 3!] thus form clampswhich hold the bars as in position when the brakes are in adjustment.The levers 3! can also be used as clamps by themselves. Thus, the plate30 can be removed and the pins 28 shortened so that the short arm of thelevers 3! bear directly against the bars 24. However, I prefer to usethe plate 3!} since it provides a larger area of Contact with the bars 2The operation of my adjuster will now be described. When the driverapplies the brakes, each brake shoe is rotated about the pivots I3 untilthe lining, 59 engages the drum. During this motion the inner edge ofthe opening 21 in the flange 18 of each shoe engages the stud Z8 and thebar 24 is moved outwardly towards the drum through the channels orguides 23. The force exerted by the wheel cylinder is sufficient to moveboth the shoes and the bars 2 3 outward- 1y even though the bars areclamped against the base 22. This leaves a space between the side of theoval stud and the outer edge of the opening which, by properdimensioning of the stud and the opening, is equal to the prescribedclearance between the shoe lining and the drum when the brakes arereleased. The width of the space is the difference between the diameterof the opening 27 in each shoe and the length of the minor axis of theoval stud. The major axis of the stud is made only slightly less thanthe diameter of the opening so as to limit vertical movement of thestud.

When the driver releases the brakes, the shoes are withdrawn from thedrumby the spring 2|. Each shoe goves inwardly away from the drum untilthe outer edge of the opening 21 contacts the stud 26. Further inwardmotion is not possible because the springs 2i do not have sufflcientstrength to move the bars 24 inwardly against the clamping action of theplate 30 and the cam levers 3!. This i due in large measure to the veryconsiderable difierence in leverage between the long arm of the lever 3|which is connected to the spring and the arm of the lever 3| whichpresses against the plate 30. It results, therefore, that the shoeswithdraw from the drum only the amount of the prescribed clearance. Asthe lining of the brake shoes wears the bars 2 will move outwardlytowards the drum when the brakes are applied until the lining pressesagainst the drum sufliciently to give good braking action. The barscannot, however,

move away from the drum when the brakes are :4 5 released, with theresult that the proper clearance between the lining and the drum isalways maintained.

From the foregoing, it is believed to be apparent that my brake adjusteris of very simple construction which will not readily get out of orderand which requires no maintenance. It will maintain the correctclearance between the brake shoes and the drum at all times. My adjusterwill also assist adriverf to stop his vehicle in case it should throw awheel. If the accident happened to a vehicle not equipped with myadjuster and the driver tried to stop the car by applyingthe brakes,fluid pressure supplied to the wheel cylinder l5 would force the pistonsIt all the way out of the cylinder and destroy the pressure throughoutthe hydraulic system in which case none of the brakes could be applied.This could not occur on cars or trucks equipped with my adjuster becausethe inner end of the slots 29 of the bars 24 would. contact the pins 28before the pistons It left the cylinder it. Pressure in the system wouldnot be lost and the driver would have available the braking action ofthe otherv wheels.

While Lhave described a present preferredembodimentof my invention, itis. to be understood that it may be otherwise embodied within the scopeof the appended claims.

Iclaim:

I l. Adjusting mechanism for brakes having a drum and. apivoted shoewhich. is applied against the drum. to obtain braking action, saidmechanism comprising abar, a lost motion connection between the bar andthe shoe permitting relative movement. between the bar. and the shoe inthe line of travel of the shoes toward and away from the drum, a clampengaging the bar andrestraining movement thereof. when the brakesarereleased and a spring secured to the shoe and to the clamp to actuatethe clamp and to withdraw the shoe from the drum when the brake isreleased.

2; Adjusting mechanism. for brakes having a drum and "a pivoted shoewhich is applied against the drum to obtain braking action, saidmechanism comprising a bar, a stud adjacent one end of the bar adaptedto extend into an opening in the shoe at a point spaced from the pivotpoint of the shoe, the dimensions of the opening and of the studpermitting limited movement of the stud in the opening, a clamp engagingthe bar and restraining movement thereof when the brakes are releasedand a spring secured to the shoe and to the clamp to actuate the clampand to withdraw the: shoe from the drum when the brake is released. 7

3. Adjusting mechanism for brakes having a drum and a pivoted shoe whichis applied against the drum to obtain braking action, said mocha nismcomprising a bar,- a stud adjacent one end of the bar adapted toextendinto an opening in the shoe at a point spaced from the pivot point ofthe shoe, the dimensions of the opening and of the stud permittingmovement of the stud in the opening, a clamp engaging the bar and restraining movement thereof when the brakes are released, and a springsecured to the shoe and to the clamp to actuate the clamp and towithdraw the shoe from the drum when the brake is released, the tensionof said spring being such as to permit movement of the bar with the shoetowards the drum when the brakes are applied.

a. Adjusting mechanism for brakes having a drum aflixed to a rotatingpart, a shoe pivoted to a fixed support and means to move the'shoe aboutits pivot to engage the drum and thereby obtain braking action, saidmechanism comprising a bar, a stud adjacent one end of the bar adaptedto extend into an opening in the shoe at a point spaced from the pivotpoint of the shoe, the dimensions or the opening and of the studpermitting movement of the stud in the opening, a base on the fixedsupport for guiding the bar, a clamp on the base pressing the baragainst the base, and a spring secured to the shoe and to the clamp toactuate the clamp and to withdraw the shoe from the drum when the brakeis released.

5. Adjusting mechanism for brakes having a drum affixed to a rotatingpart, a shoe pivoted to a fixed support and means to move the shoe aboutits pivot to engage the drum and thereby obtain braking action, saidmechanism comprising a bar, a stud adjacent one end of the bar adaptedto extend into an opening in the shoe at a point spaced from the pivotpoint of the shoe, the dimensions of the opening and of the studpermitting movement of the stud in the opening, means on the fixedsupport to support the bar and permit movement of the bar with the shoewhen the brake is applied, a clamp engaging the bar, and a springsecured to the shoe and to the clamp to actuate the clamp and towithdraw the shoe from the drum when the brake is released.

6. Adjusting mechanism for brakes having a drum aflixed to a rotatingpart, a shoe pivoted to a fixed support and means to move the shoe aboutits pivot to engage the drum and thereby obtain braking action, saidmechanism comprising a bar, a stud adjacent one end of the bar adaptedto extend into and opening in the shoe at a point spaced from the pivotpoint of the shoe, the dimensions of the opening and of the studpermitting movement of the stud in the opening, a guide on the fixedsupport in which the end of the bar opposite to the stud may move, aslot in the bar adjacent said end in the guide, a pin extending throughsaid slot, a lever pivoted on the pin and having one end adapted topress against the bar to restrain movement thereof when the brakes arereleased, and a spring secured to the other end of said lever and to theshoe to actuate the lever against the bar and to withdraw the shoe fromthe drum when the brake is released.

7. Adjusting mechanism for brakes having a drum atfixed to a rotatingpart, a shoe pivoted to a fixed support and means to move the shoe aboutits pivot to engage the drum and thereby obtain braking action, saidmechanism comprising a bar, a stud adjacent one end of the bar adaptedto extend into an opening in the shoe at a point spaced from the pivotpoint of the shoe, the dimensions of the opening and of the studpermitting movement of the stud in the opening, a guide on the fixedsupport in which the end of the bar opposite to the stud may move, aslot in the bar adjacent said end in the guide, a pin extending throughsaid slot, 3, plate in the guide adjacent the bar, a lever pivoted inthe pin and having one end adapted to press against the plate to forceit against the bar and thereby restrain movement of the bar when thebrakes are released, and a spring secured to the other end of said leverand to the shoe to actuate the lever against the plate and to withdrawthe shoe from the drum when the brake is released.

PALMER CLYDE WILSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,241,479 Rush May 13, 19412,286,711 Buflington June 16, 1942 2,463,092 Ensinger et al Mar. 1, 1949

